1. Field of the Invention
The present invention relates to a camera unit and an apparatus for monitoring a vehicle periphery.
2. Description the Related Art
For uses in a vehicle and monitoring, it is highly recommended that a wider range of visual field can be picked up by a single camera. In this case, there are many cases where it is desired that the visual field range is wider in the vertical direction than in the horizontal direction.
A camera unit having a prism at the front side of its camera and devised to pick up images in three directions are available (JP-A-2000-89301). By installing the camera unit at the front end part of a vehicle, visual field ranges A1 and A2 in the left and right directions forward of the vehicle and a diagonally downward visual field range A3 forward thereof can be simultaneously picked up as shown in FIG. 33 and FIG. 34.
An apparatus for visually confirming the rearward of the vehicle in which the rearward of the vehicle can be picked up by a camera unit using a fisheye lens is available (JP-A-7-285379).
A monitoring apparatus for a vehicle, which picks up a wide range of the periphery of a vehicle using a fisheye lens, acts and brings down a part of the picked-up image by image processing, enlarges and displays the same in a display unit is available (JP-A-2003-143596).
In JP-A-2000-89301, as shown in FIG. 33, since the visual fields A1 through A3 are limited to partial ranges in the left and right directions forward of the vehicle and a partial range diagonally downward of the front part of the vehicle, dead angle ranges B1 and B2 which are not picked up are brought about forward of the vehicle.
In JP-A-7-285379, since the visual field is simply enlarged by using a fisheye lens although the visual field is enlarged by the fisheye lens and the dead angle ranges rearward of the vehicle are reduced to be narrow, distortion in the picked-up image is increased, for example, as in the part C1 surrounded by a hypothetical line in FIG. 35, wherein visual confirmation is lowered. Also, for example, as in the part C2 surrounded by a hypothetical line in FIG. 35, an object is picked up to be small, and it becomes a cause of a lowering in visual confirmation. Further, for example, as in the part C3 surrounded by a hypothetical line in FIG. 35, the semi-celestial sphere is picked up by a fisheye lens, wherein unnecessary light rays such as sunlight, streetlights, etc., are apt to be picked up by a pickup element, the brightness adjustment of a camera fails (that is, if a bright object is taken, the camera aperture is adjusted to become dark). In addition, a ghost image, flare, etc., occur due to the unnecessary light, wherein visual confirmation of images is further worsened.
Further, in JP-A-2003-143596, since the number of pixels of the camera is limited, the image is made coarse if it is enlarged by an image process, visual confirmation is lowered. That is, the resolution power of a picked-up image is determined by the number of scanning lines of NTSC. In particular, image deterioration due to an enlargement process is more remarkable in the vertical direction than in the horizontal direction. Also, in a normal fisheye lens, a picked-up image is taken to be smaller in the peripheral portions than at the central portion due to distortion, wherein if the peripheral portions of the picked-up image are enlarged, the image deterioration becomes particularly remarkable.